1. Field of the Invention
The present invention relates to a mechanism for securing recorded contents of a recording medium cassette whether or not it has a memory and, more particularly, to a mechanism for ensuring that recording information stored in the memory of the recording medium cassette always matches contents recorded on a recording medium of a recording medium cassette.
2. Description of the Prior Art
A variety of recording medium cassettes having memory have been proposed. See for example a patent to Staar U.S. Pat. No. 4,338,644 for "Magnetic Tape Cassettes Provided with Memory Circuits for Storing Information," issued Jul. 6, 1982. Such cassettes are often referred to as MIC cassettes (MIC is an acronym for "memory in cassette"). If these memory-based recording medium cassettes are put in the market, there will be both types of recording medium cassettes at the same time: memory-based type and non-memory type.
At the same time, there will be both types of recording/reproducing apparatus: one compatible with a memory-based recording medium cassette and the other incompatible with a memory-based recording medium cassette. Possible combinations of these cassettes and recording/reproducing apparatus will be as shown in Table 1.
TABLE 1 ______________________________________ Recording/reproducing apparatus Recording medium cassette For memory Not for memory ______________________________________ With memory A B Without memory C C ______________________________________
The memory installed on a recording medium cassette stores character information about contents recorded on the cassette as well as other information such as recording time and date. It is therefore essential that there exist a correlation between the information stored in the memory and the contents recorded on the cassette. However, in a situation where there are a recording/reproducing apparatus suitable for a memory-based recording medium cassette and a recording/reproducing apparatus not suitable for such a cassette at the same time as shown in Table 1 above, there is a possibility, as described below, that the contents recorded on the cassette will not correspond to the recording information stored in the memory.
"A" in Table 1 is the combination of a memory-based recording medium cassette and a recording/reproducing apparatus suitable for such a cassette. As FIG. 14 shows, there exists a complete match between contents 15a, 15b, 15c, 15d and 15e recorded on a recording medium 15 of the recording medium cassette and information 16a, 16b, 16c, 16d and 16e stored in a memory 16 of the recording medium cassette. Thus, there is no problem in retrieving desired data.
"B" in Table 1 is a combination between a memory-based recording medium cassette and a recording/reproducing apparatus incompatible with such a cassette. Referring to FIG. 15, there may not be a complete correlation between contents 17a, 17b, 17c, 17f and 17g recorded on a recording medium 17 and the information 16a, 16b, 16c, 16d and 16e stored in the memory 16. That is, since this recording/reproducing apparatus is incompatible with the memory, recorded contents 17f and 17g do not match the information 16d and 16e stored in the memory.
"C" in Table 1 is the combination of a recording medium cassette without a memory and a recording/reproducing apparatus compatible with a memory or a recording/reproducing apparatus incompatible with a memory. In this case, there is no problem of a mismatch between recorded contents and recording information. As FIG. 16 shows, since no memory is provided, the recording/reproducing apparatus does not know the start point of 18e.
Thus, if a recording medium cassette with a memory and a recording medium cassette without a memory exist together and, additionally, a recording/reproducing apparatus compatible with the recording medium cassette with the memory and a recording/reproducing apparatus incompatible with such a cassette exist together, there is always a chance of a mismatch between the information stored in the memory of a recording medium cassette and the contents recorded on the recording medium of a recording medium cassette. In that case, if a recording medium cassette having such a mismatch is used on the memory-compatible recording/reproducing apparatus and the contents in the memory are read, the mismatch causes confusion in a data retrieval operation, and the value added by the memory is lost.
Besides, there are two conventional types of mechanisms for protecting information recorded on a video tape cassette. One, employed on video tape cassettes of VHS type and Beta type, uses a protection tab removably attached on the rear or bottom side of the cassette. Normally, a write protect opening provided on the rear or bottom side of the cassette is closed with this tab, enabling the writing of data on the magnetic tape. When this tab is removed, the write protect opening is exposed to prevent a data write operation.
The other, employed on a video tape cassette of 8-mm type, uses a slidable tab on the rear side of the cassette. The tab slides over a write protect opening provided in the bottom of the cassette to close the opening, thereby enabling a write operation. When the tab slides in the other direction, it exposes the opening and protects recorded data from being erased or overwritten.